1. Field of the Invention
The present invention relates to a radiographic image processing method, a radiographic image processing apparatus, a radiographic image processing system, a program, a computer-readable storage medium, an image diagnosis assisting method, and an image diagnosis assisting system.
2. Description of the Related Art
Techniques for utilizing the ability of radiation such as X-rays to pass through many or most materials, and imaging a distribution of transmittance of the radiations have been the basis for development of a great deal of modern medical technology. Since the discovery of X-rays, a distribution of X-ray intensity has been imaged by a method of converting the distribution of X-ray intensity to visible light with a phosphor, forming a latent image on a silver-salt film with the visible light, and then developing the latent image. Recently, when obtaining an X-ray image in digital form, a method employing the so-called imaging plate has been popularized, in which a photostimulable phosphor is used to form a latent image representing a distribution of energy accumulated in the photostimulable phosphor upon irradiation by X-rays, and a laser beam illumination is used to excite the photostimulable phosphor to read the latent image, thus obtaining a digital image. Further, with the progress of semiconductor technology, a large-sized solid-state image pickup device capable of covering the size of a human body, i.e., the so-called flat panel detector, has been developed and has contributed to directly digitizing an X-ray image without forming a latent image, and thus to realizing more efficient diagnosis.
Meanwhile, with development of a highly-sensitive image pickup device utilizing an image intensifier, it has become possible to form an image of fluorescence generated with weak X-rays and to observe a moving state of the interior of a human body. This method has also been put into general use. Then, the latest flat panel detector has sensitivity comparable that of the image pickup device utilizing an image intensifier, and has become applicable to radiographing a moving state of even a large region or portion of a human body.
The most effective radiography in medical use is radiography of the chest of the human body. Radiographing of a wide region, including the chest, but covering the abdomen as well, is useful for discovering many diseases, including lung diseases, and therefore radiographing of the chest is essential in standard health examination, e.g., a general physical examination. Also, in order efficiently to diagnose a large amount of X-ray chest images radiographed for health examination, so-called Computer-Aided Diagnosis (CAD) has been recently put into practice, in which digital X-ray chest images are analyzed using a computer so as to assist doctors in initial diagnosis.
In diagnosis, it is effective to obtain a moving-state image of the chest, which represents a moving state due to breathing, etc., using the above-mentioned large-sized flat panel detector and to observe the moving state.
However, diagnosis based on a still image (film) representing the maximum inhalation state of chest is a reliable diagnosis method that has been practiced for many years, and doctors are well experienced in the diagnosis based on the still image. Conversely, it is probably thought that, in not a few cases, doctors cannot sufficiently recognize information useful for diagnosis that could be obtained from observing a moving-state image of the chest. Further, because the moving-state image is generally radiographed with a small dose, reliability of detailed image information obtained in this fashion is relatively low. Hence, diagnosis information based on the conventional still images remains very important.
In addition, conventional CAD for a general radiograph of the chest has been usually performed on one radiographed image. This is attributable to the fact that there has been only a generally radiographed still image as an image for use in initial diagnosis. Consequently, the amount of information available in CAD is small, which has been one factor causing a stagnation in detection accuracy of the CAD.